Azeotropic distillation of aqueous isopropanol contaminated by acetone



Sept. 6, 1949.

- M. c. FUQUA 2,481,211 AZEOTROPIC DISTILLATION OF AQUEOUS ISOPROPANOLCONTAMINATED BY ACEIONE Filed May 22, 1946 ETHEl-VAQETONE '20 W a2 2,.ETHEK r22 1G lfiQPROPYL LCOHQDL. ETHmL' 4.2 47

+ Auuvo'aous ALCOHOL.

917 lQPRQPYL- ALCOHOL mac C. Fuqua :Snvenbor gMClL-boraeg propyl alcoholwith Patented Sept. a, me

AZEOTROPIC DIS mom or neurons IEdQfiPEBOPANOL CONTAMINATED BY AGE- k c.Fuqua, Baton Rouge, designer to Standard Oil e Claims.

he appears in the product because of the abnormal behavior of theacetone. If the an.- hydrous product is desired, simple distillationdoes not result in the recovery of anhydrous alcohol,

dehydrated and the water. is distilled oii and allowed to separate intotwo layers upon condensation. The aqueous phase is discarded and theentrainer is returned to the still. Suitable entrainers used in the artinclude hydrocarbons, ethers, carbon tetrachloride, etc. It impuritiesare present, the difiiculties are often increased.

For example, it is This ternary mixture trainer.

Development poration oi Delaware Application May 22, rate. den-tall No.

@mnpeny, a cor- 671L583. (m. Elm-d2) can be appreciated by acomperison'of the 5 lowing data.

Tessa I Composition of ternary azeotrope of isoprom'l ether-isopropylalcohol-water M Distilled at 760 mm. Hg. Phases separated at C.

U per Lower Com- L yer Layer bined Weight percent Isopropyl Alcohol. 7.2 9. 8 7. 3 15 Weight percent Isopropyl Etheix... 91. 7 Trace 88.0Weight percent Water l. l 90. 4. 7 eight percent Layen- 96. 0 4. (l0. 0Boiling Point, C 61. G

From the abo 26 the feed, the acetone content of the overhead will buildup substantially, requiring a large quantity of heat, excessivedistillation and condensation equipment.

3 What has been the distillation of any other organic oxy compoundscontaining a contaminant whisk iiiterferes with the separation of phasesin the distillation. I

It is, therefore, the main object of this inven-- tion to provide aprocess for the distillation of organic'oxy compounds in which theeiiects of contaminating substances is minimized or completely overcome.

It is a further objectof this invention to prc-= vide a process for theremoval of contaminating process is particularly eflective in connectionwith the .cohol with isopropyl ether it is not intended to removingacetone as a contaminant in the distillation of isopropyl alcohol usingisopropyl ether as the entraining agent. According to this embodiment ofthe process, aqueous isopropyl alcohol is distilled in the presence of asmall amount of isopropyl ether sufficient to completely remove acetoneoverhead as a ternary azetrope with water. The overhead productcontaining the ether and acetone is discarded. Aqueous alcohol, freefrom acetone, is removed from the bottom of the still and if anhydrousisopropyl alcohol is desired, the aqueous product is subjected to asecond azeotropic distillation with sufflcient isopropyl ether to efiectremoval of all the water.

In order that the invention may be fully understood, reference is madeto the attached drawing as one method of carrying out the process of thepresent invention.

A binary azeotrope of isopropyl alcohol and water in the ratio of 91:9volume per cent and containing 0.46 per cent by weight of acetone isintroduced into distillation tower through line H. About 0.1 per cent byweight isopropyl ether, based on the alcohol and water, is initiallyadded through line 12 and subsequently is used to insure the formationof the ternary azeotrope with water and acetone. This ternary azeotropeis removed as vapor overhead through line l3 and discarded.Substantially 91% alcohol free from acetone is removed from the bottomof tower l0 through line ll. This product is suitable for marketing assuch but if it is desired to produce the anhydrous product, it is passedto dehydration tower l8 and mixed with about ten volume per cent ofisopropyl ether based on the aqueous alcohol initially introducedthrough line l9. Additional amounts may be added as needed to insure theformation of a ternary azeotrope of isopropyl alcohol, water and ether.

line 20, cooled in condenser 2| and collected in decanter 22 where theseparation of phases results. The upper non-aqueous phase containing theisopropyl ether is returned to tower l8 through line 23, while the loweraqueous phase is discarded. Anhydrous alcohol is removed from the bottomof tower it through line 24.

The following table illustrates the advantages of small amounts ofisopropyl ether in removing acetone from aqueous isopropyl alcoholsolutions.

TABLE II f A l B Overhead,

Volume, Acetone Acetone in Acetone Acetone in Per Cent in 0. H. Bottoms,in 0. H. Bottoms, Weight, Weight, Weight, Wei ht, Per Cent Per Cent Pcrent Per ent 9.6 0. 33 10.0 0.16 5. 4 y 0. 23 3.4 0.09 l. 8 0. 12 l. 9 0.07 l. 4 (l. 07 0. 9 0. 04 0. 6 0. 0. 8 U. 02 0. 4 0. 04 0. 2 0. 00 0. 20. 02 0. 1 0. 00 0. 1 0. 00 0. 07 0. 00 O. 07 0. 0O 0. 05 0. 0O 0. 020.00 0. 02 0. 00

A- 9l volume per cent isopropanol contained 0.46 weight per centacetone.

B-Ql volume per cent isopropanol contained 0.46 weight percent acetoneplus 0.1 weight per cent isopropyl ether.

While the above process has been described in distillation of isopropylal- Vapors of the ternary azeotrope are removed overhead through be solimited. The process of the present invention is intended to cover theremoval of contaminating materials present in small amounts in anorganic liquid being distilled and is particularly adapted to theremoval of such contaminating materials from organic oxy compounds whenethers are used as the dehydrating agent as described in U. S. 2,140,694issued December 20, 1938 to Theodore Evans. For example, dinormal propylether, dinormal butyl ether, di-isobutyl ether, disecondary butyl ether,ditertiary butyl ether, symmetrical normal, iso, secondary and tertiaryamyl, hexyl, heptyl, octyl and the like ethers may be employed asentraining agent in each step depending upon the particular compoundbeing distilled.

The nature and objects of the present invention having been thus fullyset forth and specific examples of the same given, what is claimed asnew and useful and desired to be secured by Letters Patent is:

1. In a process-for the separation of water from aqueous isopropylalcohol by azeotropic distillation with an entraining agent wherein thed stillate separates into two phases and wherein the aqueous alcoholcontains acetone which interferes with the separation into phases, theimprovement which comprises removing the acetone from the aqueousalcohol by a preliminary distillation in the presence of a small amountof isopropyl ether sufficient only to remove the acetone as anazeotrope.

2. Process for removing acetone from aqueous isopropyl alcohol solutionscontaining approximately 0.46 wt. acetone comprisin subjecting theaqueous isopropyl alcohol containing the acetone to an azeotropicdistillation with 0.1% by weight of isopropyl ether.

3. A process for the removal of acetone from an aqueous solution ofisopropyl alcohol containing approximately 0.46 wt. acetone whichcomprises mixing the aqueous isopropyl alcohol and acetone with 0.1% byweight of isopropyl ether based on the aqueous alcohol, distilling themixture to drive off an azeotrope comprising ether, water and acetone,discarding the vapors of the azeotrope and continuing the distillationuntil acetone is no longer removed overhead.

4. A process according to claim 1 in which the aqueous isopropyl alcoholcontains approximately 0.46 wt. acetone, in which the isopropyl etherentrainer is used in amounts of 0.1 wt. in the acetone removal step, andin amounts of 10 volume in the dehydration step.

5. In a process of purifying isopropyl alcohol contaminated by a smallamount of acetone in aqueous solution thereof, the improvement whichcomprises subjecting the contaminated aqueous solution of isopropylalcohol to distillation in a fractional distillation zone with a smallamount of admixed isopropyl ether, removing overhead from said zone anazeotropic vapor mixture of acetone with said ether, and withdrawingisopropyl alcohol free of acetone as bottoms from said fractionaldistillation zone.

6. A process for the purification and dehydration of isopropyl alcoholcontaminated by a small amount of acetone in aqueous solution thereof,which comprises subjecting the contaminated aqueous solution ofisopropyl alcohol to distillation in a first fractional distillationzone with a small amount of admixed isopropyl ether, removing overheadfrom said first fractional distillation zone an azeotropic vapor mixtureof acetone with said ether, withdrawing aqueous alcohol free of acetoneas bottoms from said fractional distillation zone, passing said aqueousalcohol into a second fractional distillation zone, admixing 6REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 1,702,495 Clapp Feb. 19, 19292,140,694 Evans Dec. 20, 1938 OTHER REFERENCES Analytical Chemistry,August 1947, copy in Scientific Library, page 537.

